What Molten Metal Deposition (MMD) brings to aluminum AM

Aluminum is everywhere in society and one of the most widely used metals in the world. Despite this, the material has been something of a weak spot within metal additive manufacturing. The metal, characterized by high reflectivity and thermal conductivity, has presented processing challenges across metal AM technologies like powder-bed fusion and binder jetting. 

And while advances have been made in aluminum 3D printing, most have been focused on printability, prioritizing easier-to-print aluminum alloys like AlSi10Mg rather than those that are more standardized across industries like aerospace, automotive, and construction. 

Belgium-based ValCUN has presented a technology that overcomes many of the limitations of 3D printing aluminum: Molten Metal Deposition (MMD). The technology offers users a single-step production approach that is compatible with off-the-shelf aluminum wire feedstock, does not require complex heat treatments or post-processing; and results in strong, crack-free parts. 

How MMD works

ValCUN’s proprietary MMD technology is based on a metal extrusion process that uses a heated nozzle to extrude molten aluminum onto a substrate secured on a heated bed. Comparable to polymer-based FDM, MMD effectively builds parts layer by layer, using aluminum wire feedstock instead of filament, which cools into a fused, solid state. 

The single-step process, which does not require any debinding or sintering, feeds pure aluminum wire feedstock into an electrically heated crucible. In this chamber, the feedstock is heated to about 700°C until it softens into a molten state and is subsequently extruded through a nozzle using controlled volumetric extrusion to ensure precise deposition. 

The build material is consistently kept at the right viscosity (i.e. molten state) thanks to the unique printhead and crucible design. As the company explains, its system uses bulk heating of the crucible to achieve a more predictable thermal profile characterized by lower maximum temperatures and lower thermal gradients. 

When the extrusion process is complete, the finished part can be easily removed with the substrate from the heated bed, and taken off the substrate “in one snap”. In the meantime, a new substrate can be applied to the printer within seconds, allowing for continuous productivity. 

ValCUN emphasizes that printed parts are ready to go once the extrusion is complete. In short, the molten extruded feedstock hardens into a solid-state structure that requires no additional heat treatments such as HIP. As it says: “What comes off the substrate is dimensionally stable and structurally coherent.”

Post-processing steps like machining can, however, be employed to achieve tight tolerances and smooth surface finishes. MMD also enables a high level of design freedom and support-free printing—uncommon for extrusion-based AM—as the process’ controlled cooling enables features like 75° overhangs and more than 25 mm bridges. In a video demonstration, for instance, ValCUN 3D printed a coiled aluminum Christmas tree in bridging mode, demonstrating how parts can be printed without supports.

The benefits, from safety to material choice

Commercialized in the Minerva Printer, the MMD process offers a range of benefits when it comes to aluminum AM. For starters, ValCUN’s approach translates to an overall safer and simpler additive manufacturing process, which does not require the use of high energy sources, like beams or lasers; does not require debinding or sintering; and eliminates risks associated with powder-based AM, such as oxidation, contamination, or explosion. 

This also means that the technology can be implemented without any auxiliary equipment, like powder management or debinding and sintering hardware. In fact, the MMD process comes with minimal infrastructure requirements. The system, which has a compact footprint, can be used in ambient air or local inert atmosphere, eliminating requirements for vacuum chambers or inert gas purging. If needed, machining can be used alongside the technology to achieve tighter tolerances.

“Unlike beam-based systems that rely on complex energy calibration, Molten Metal Deposition simplifies the entire thermal model,” ValCUN says. “There’s no laser, no arc, no melt pool to manage. The material is already molten. Instead of controlling energy input, the process focuses on deposition and cooling, avoiding many of the failure modes associated with beam-based printing.”

Another key selling point for ValCUN’s solution is that it is compatible with standard industrial aluminum alloys, including Al 4008, Al 4043, and Al 5082​. This means that end users can print from standardized materials without having to test and validate alternative alloys. (Other aluminum alloys like Al 6061, Al 6082, and Al 7xxx are also in the pipeline.) The company also states that other materials are being qualified (Magnesium, Copper, Silver, Gold, Steel) and that customers can make requests for specific alloys. 

As ValCUN writes: “By extruding aluminium in its molten state, MMD eliminates the friction that kept the material on the fringe of AM. As a result, for the first time, standard industrial alloys, not just printable variants, can be used safely, economically and without compromise… The result is tighter alignment between prototyping and production: one alloy, one process, one outcome.”

Compared to other wire-based additive manufacturing processes, such as WAAM, which are compatible with off-the-shelf aluminum alloys, ValCUN says its MMD process offers greater precision and design freedom, requiring less post-processing.  

MMD applications

Molten Metal Deposition (MMD) is viable for a range of use cases and demonstrates particular value in industries where aluminum use is standard and alternative AM approaches have presented limitations for certain applications. These industries include:

• Aerospace and defense (i.e. brackets, antenna supports, payload enclosures, UAV airframes)
• Automotive (i.e. heat exchangers, pump housings, custom ducting)
• Electronics (i.e. heatsinks, cold plates, housings)
• Architecture and design (i.e. lighting, façade structures, sculpture)

For these industries, the combination of MMD technology (capable of producing complex, stress-free parts) and aluminum’s inherent properties (such as low weight, good thermal transfer, and electrical conductivity) enable the production of functional prototypes and end-use components on demand. Moreover, MMD parts can be welded, which gives manufacturers the freedom to weld printed aluminum components to aluminum sheets or other aluminum structures for cost optimization. 

ValCUN has identified MMD’s most profitable use case as thermal management components, which benefit from complex internal geometries and aluminum’s high thermal conductivity. According to ValCUN, printed thermal management components like fan blades have demonstrated 30% less power losses compared to extrusion components thanks to the design freedom needed to obtain an optimized airflow. This application area could be particularly impactful for data centers, as well as for electronic vehicles and other power electronics cooling projects.  

ValCUN also recently demonstrated MMD’s potential for printing catalytic air purifiers. Working in collaboration with Addcat, the company 3D printed a complex aluminum substrate for catalytic materials, which resulted in a 37% total cost of ownership reduction and a 20% improvement in catalytic efficiency thanks to a maximized catalytic surface area.

An alternative for aluminum AM

Overall, ValCUN has presented a compelling new approach for producing aluminum parts that overcomes many of the challenges associated with other 3D printing methods. Molten Metal Deposition, as a one-step metal AM process, facilitates the manufacturing of complex, structurally stable components while also simplifying internal production processes. As we’ve seen, the process enables manufacturers to 3D print standardized aluminum grades, cut out time-consuming steps (like debinding, sintering, and heat treatments), and avoid the use of powder management infrastructure. 

As ValCUN puts it: “The barrier to printing aluminium wasn’t a lack of innovation. It was a mismatch between material and method. For years, additive manufacturing has tried to force aluminium into processes that were never suited to its properties. Molten Metal Deposition corrects that.”